1. Assoc. Prof. of Operations Research, Dept. of Mechanical and Industrial Engrg., Univ. of Illinois at Urbana-Champaign, Urbana, Ill. 61801
2. Dept. of Engrg., Chulachomklao Royal Military Academy, Bangkok, Thailand
3. Prof. of Civ. Engrg., Univ. of Illinois at Urbana-Champaign, Urbana, Ill. 61801